1. Technical Field
The present invention relates to a method of manufacturing a semiconductor device making use of a shadow ring, and an etching apparatus.
2. Related Art
A shadow ring is occasionally used for an etching apparatus or a film-making apparatus used for manufacture of semiconductor devices. The shadow ring is a ring-form component disposed so as to cover a circumferential portion of a substrate, aimed at preventing a certain width of region ranging from the edge of the substrate from being etched or deposited with any film (see Japanese Laid-Open Patent Publication Nos. 2002-294441 and 2006-118004, for example). Without the shadow ring, the process would have an increased number of steps in the manufacturing, including a step of grinding the circumferential portion of the film so as to remove the deposited film.
One step of using the shadow ring is known as a step of forming relatively deep trenches or holes to a layer to be etched. This step is such as forming a hard mask, typically composed of a silicon oxide film, on the layer to be etched, and then etching the layer using the hard mask as a mask. In this step, there is no hard mask formed in the circumferential portion of the layer to be etched, for the purpose of preventing generation of foreign matters from the hard mask in the process of handling. The shadow ring is used to protect the circumferential portion of the layer to be etched during etching.
On the other hand, Japanese Laid-Open Patent Publication No. 2002-334879 describes a technique of forming a protective film on an insulating film formed on a wafer, specifically in the bevel region thereof in order to protect the insulating film in the bevel region.
The hard mask is removed by etching, after the trenches or holes are formed. However, in this process, also the circumferential portion of the layer to be etched is slightly etched. For this reason, the layer to be etched may be roughened in the circumferential portion, if the etching for removing the hard mask takes a long time.